The invention relates to a dynamic groove bearing comprising an internal bearing part and an external bearing part which can be rotated relatively to each other about an axis of rotation, a bearing surface of one of the bearing parts being provided with two groove patterns for co-operation with a bearing surface of the other bearing part, which groove patterns, viewed parallel to the axis of rotation, are spaced apart, and the groove bearing being provided with a reservoir made from a porous material for holding a lubricant which, in operation, is present between the co-operating bearing surfaces.
The invention further relates to an electric motor comprising a stator and a rotor, which is mounted so a to be rotatable with respect to the stator by means of a dynamic groove bearing.
The invention also relates to a scanning device provided with a support for an information carrier and a scanning unit for scanning the information carrier, said support being rotatable about an axis of rotation by means of an electric motor, while the scanning unit can be displaced with respect to the support at least in a direction transverse to the axis of rotation by means of a displacement device.
A dynamic groove bearing of the type mentioned in the opening paragraph is known from JP-A-08322191. The internal bearing part of the known groove bearing is a shaft, and the external bearing part of the known groove bearing is a bush, the shaft being rotatable in the bush. The groove patterns of the known groove bearing are provided on the shaft. During rotation of the shaft in the bush, the groove patterns generate an overpressure in the lubricant which is present between the co-operating bearing surfaces of the shaft and the bush, so that the shaft is supported in a direction perpendicular to the axis of rotation. The reservoir of the known groove bearing comprises two ring-shaped bodies which are made from a sintered metal and are each secured in the bush near an end of the bush. By using the reservoir, a quantity of a lubricant is present in the known groove bearing, which quantity is much greater than a quantity of lubricant present between the co-operating bearing surfaces. As a result, ageing of the lubricant, which is predominantly caused by a chemical reaction between the lubricant and the bearing metals used in the groove bearing, is retarded considerably, so that the known groove bearing has a much longer service life.
A drawback of the known dynamic groove bearing is that there may be a difference between the quantities of lubricant present in both porous ring-shaped bodies, as a result of which there is a different lubricant supply to both groove patterns, which leads to improper operation of the groove bearing. In addition, the known dynamic groove bearing comprises a relatively large number of parts, which can be attributed to the use of the two porous ring-shaped bodies.